1. Field of the Invention
The present invention relates to a distributor type fuel injector employing a system whereby a cam ring with a cam surface (cam lobes) formed on its internal circumference is provided around a rotor to cause plungers provided at the rotor to move reciprocally in a radial direction to vary the volumetric capacity of a compression space.
2. Description of the Related Art
Inner cam system distributor type fuel injectors in the prior art employ a basic structure in which a cam ring with a cam surface (cam lobes) formed on its inner circumference is provided around a rotor, plungers are provided slidably in the direction of the radius of the rotor and the plungers are caused to move reciprocally in the direction of the radius by the cam surface (cam lobes) of the cam ring as the rotor rotates, as disclosed in, for instance, Japanese Unexamined Patent Publication No. S 61-237840 and Japanese Unexamined Patent Publication No. H7-247932. In this basic structure, the cam ring, which is held by a housing, is caused to rotate in the circumferential direction by a timer mechanism provided below it.
While the housing comprising the fuel injector is constituted of an aluminum alloy or the like to achieve a reduction in weight, the cam ring itself is constituted of steel or the like in order to increase the hardness. Because of this, the cam ring may become seized in the housing due to different coefficients of thermal expansion of the various members in cold weather. Therefore, in the structure in the prior art described above, the housing and the cam ring are designed to have sufficient clearance between them to prevent this from happening.
However, in the structure described above, in which the clearance between the housing and cam ring must be set large in consideration of the varying coefficients of thermal expansion in different members, some axial misalignment tends to occur between the cam ring and the rotor, resulting in vibration in the cam ring during operation of the fuel injector. This, in turn, leads to problems such as increased impact noise caused by the cam ring coming in contact with the housing and wear on the contact surfaces of the cam ring and the housing.
In addition, in the prior art technology described above, the cam ring and the timer mechanism are linked together by a separate connecting rod. If the clearance is increased, however, the load on the connecting rod is increased, making it difficult to achieve sufficient connection strength.